oal measered from the ogive

3

308Loader

New member
Hi again every one. Still kind of new at reloading. This is my 2nd year reloading for my rem 700 in .308. recently I picked up a bullet comparator and oal gage. I measured the distance to my lands with 168gr hpbt bullet.

distance =
2.312
2.311
2.313
2.311
added up (9.247) and divided by 4 to get an average of 2.31175 rounded up to 2.312. What I have ben reading is one wants about .002 off the lands so -.002= 2.310. this looked ridiculously long and to add margin of safety I rounded down to 2.300 or .012 from the lands (all measurements taken from the ogive of the bullet.) So when seated a complete cartridge is 2.905 measured from the bullet tip to case head. I ran a few through my bolt and it seems fine, no rifle marks at tip of bullet... These will definitely not fit in the internal mag but im ok with that because this is just for target shooting. So my question is did I just waste your time (for reading this) and mine for finding that reaching my lands may not be possible without f-ing up neck tension and seating my bullet WAY out their. The few I loaded should be safe to shoot right?
 
What I have ben reading is one wants about .002 off the lands
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Are you sure you aren't thinking 0.020" off the lands as a normal staring point? I use the 20 thousandths as my starting point UNLESS:

- I don't have at least 1/2 bullet diameter for bullet seating depth
- I intend to magazine feed and they are too long
- If I find I get better accuracy with a seating depth different than my standard 0.020"
 
I'm like jepp and I always start at .02" off the lands. Shoot my workup. Once I find my best charge I'll start fine tuning by adjusting bullet depth.
 
OMG! Yes, in reading through my notes I did read the writing wrong and wrote it down wrong. embarrassing, thanks.
 
I have been working 308 rounds recently and found that a higher charge with the ogive touching (jammed) causes issues. My issue is that my primers will fall out of the cartridge after being fired. What I have gathered from other members is that the case pressure builds too high when touching the lands. I backed off the lands .020 and had no issues. I still have to work it to find the sweet spot. My load was 43 Grains 4064 using hornady match cases with hornady 168 boat tail and Winchester primers. Just shot out to 881yrds last weekend and did well.
 
Study long, study wrong. I am the 'off the lands' fan. I am the fan of the running start, I want my bullets to have 'the jump'.

If my rifle does not shoot good with the running start I shoot something that does. I do insist on knowing the distance from the bolt face to the rifling. I have tested chambers that were too long, one that comes to mind was a 7mm Wildcat. I pushed the bullet out of the case, down the throat and then finally the bullet hit the lands. The confused and proud builder of the rifle ask "What caused that?", and I had to say, "I do not know".

He wanted to know why the rifle did not shoot as good as the other 4 he built, and of course, I did not know. We loaded 100 rounds for the rifle and went to the range. There was a narrow window of loadings that could not be improved upon. There was no tweaking.

When determining the distance from the bolt face to the rifling I make transfers, I make once transfers meaning I do not do it over and over and over, I do it once.

F. Guffey
 
So my question is did I just waste your time (for reading this) and mine for finding that reaching my lands may not be possible without f-ing up neck tension and seating my bullet WAY out their. The few I loaded should be safe to shoot right?
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You'll need to be the judge of whether your particular bullet can get to .02 off and still have enough meat in the case (typically, about the diameter of the bullet as a mimimum). With the SAAMI chamber and a 168, it shouldn't be a problem.

OTOH, we have a rifle chambered in .260 Match, which has .042 more freebore than the Remington spec. It was designed for the 6.5 heavies, which needed to be seated too deeply into the case when used with the standard .260 freebore.

While not your case, shooting heavies/VLD's from standard throated chambers can be problematic for long-range shooters.
 
f-ing up neck tension
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I can not help you with neck tension, I do not have neck tension, I can not measure neck tension, many years ago I started with 'bullet hold', I can measure bullet hold in pounds 'make that push and pull' but not tensions and I do not have a conversion that takes me from tensions to pounds.

I want all the bullet hold I can get. I want the powder behind the bullet to have a chance to get started.

F. Guffey
 
There is no magic seating for accuracy. I have had gun that it flat did not matter how far off the lands the bullet was they all shot the same. I have had a few gun that would shoot real good with .050 to .100 of the lands, ( not many) and other that shoot best with the bullet jammed into the lands to the point it would pull the bullet if you tried to eject a loaded round. I will tell you that if you try loading into the lands your pressure curve goes up very fast and and you will need to load a few grains less than with the bullet a few .001`s off the lands. Mostly, heavy for caliber bullets are more accurate very close or into the lands. But that is not always true ether.
 
Got to go shooting today:). I seated the rounds to the right depth .02 off the lands witch turned out to be 2.292, shot great. Noticeable improvement from the way I measured before. Would this measurement be a good starting point for me to seat other bullets like vld or ballistic tip? Or is it best to measure everything again for each.
 
Each bullet has its own profile. You'll need to measure again when changing bullet to start .02" off lands.

And remember it's always best when changing bullets to start all over again with a new workup.
 
Or is it best to measure everything again for each.
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I will never understand how a reloader can determine the distance from the lands to the bolt face without knowing the diameter. In the perfect world the two diameters of my 30 cal. barrels measure .308" and .300", I have no problem jamming a bullet down the barrel when measuring the diameter or measured from point.

I know, variations, and all the reasons it can not be done. For those that can not do it, start over every day.

F. Guffey
 
It varies by bullet. Secant ogives typically like to be jammed. Just how much is for you to work out. Tangent ogives typically like a bit of jump. This is not an absolute truth. Your barrel is the ultimate decision maker.

Good luck,
 
Secant ogives typically like to be jammed.
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I always thought so, too- as did Berger.

Now, they say it ain't always so...and offer their methodology for determining best jump.

http://www.bergerbullets.com/vld-making-shoot/

What I don't like about this, is that jamming a bullet into the rifling increases pressures- and looking for pressure signs here as loads get hotter would definitely be even more important than usual.
 
Your barrel is the ultimate decision maker.
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I am the fan of the running start, I want my bullet to have 'the jump'. If my rifles do not like the jump and or running start they never get the chance to sit at the rifling when the trigger is pulled, just sitting there trying to decide if they are going to take off or cause a scene.

F. Guffey
 
There is simply no way that I am aware of to avoid experimenting with your particular rifle, IF YOU WANT MAXIMUM ACCURACY.

I normally seat .010 off of the rifling for most rifles if the magazine (and bullet) allows it.. One of my heavy barrel 6MM varmint rifle demands that the bullet actually touch the rifling lightly. (Remington 40XB-BR single shot bolt action with Shilen barrel)

My heavy barrel custom Sako/Krieger .223 bolt action likes them clear back to .025.

Unless you have a special need for varmint/benchrest accuracy levels, anywhere from .010 to .0025 should work well for you and give very acceptable accuracy.:)
 
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